Mike Bartusiewicz, Dong-Hyun Chung, Steve Cullen, Kate Horlocker, Na Ning, & Bin Tong The Leaning Tower
• Construction of Tower began in 1173 under supervision of architect Bonanno Pisano
• Bell tower was built as manifestation of city’s pride and was meant to reflect rich city of Pisa
http://www.pubs.asce.org/ceonline/ceonline02/0302feat.html Construction of The Tower
• Work on Tower ceased in 1178 for reasons unknown; studies have shown that soil on which Tower was built would not have been able to withstand more construction at that time
• Construction began again, but ceased in 1278
• Had Tower been completed at this time, would have collapsed because of the stress on soil http://www.pubs.asce.org/ceonline/ceonline02/0302feat.html http://www.costruzioni.net/images/pisa.h4.jpg Construction of The Tower
• During actual construction of Tower in 1100’s, Tower originally leaned north – Masonry blocks placed on each level to correct lean of axis
• By end of its construction, the Tower leaned significantly to the South
• Tower was finally completed in 1370; height is 53 m
http://www.electricedge.com/greymatter/archives/archive-10052003-10112003.htm http://www.pubs.asce.org/ceonline/ceonline02/0302feat.html The Leaning Tower Today
• From early 1990 until December 2001, Tower was closed to public because of safety issues • Italian engineers implemented complex $25 million rescue plan in order to stabilize Tower • Although Tower looks as if it might collapse at any moment, in reality, it is more stable now than at any time in past few centuries
http://www.pubs.asce.org/ceonline/art/art02/0302feat1.jpg Alternatives to Restoration • In 1838, architect Alessendro della Gherardesca constructed a walkway around Tower base
• Water filled the walkway area after the excavation extended below water table
• Plan increased tilt of Tower by over one quarter of a degree
• Gherardesco placed 0.7 meter thick ring of concrete around walkway to help stabilize Tower, but excavation nearly caused its downfall Alternatives to Restoration • In 1934, engineers used grout injection to stabilize the foundation of Tower
• This process led to a displacement of Tower
•The tip of Tower tilted 10 mm more to South
http://www.pubs.asce.org/ceonline/ceonline02/0302feat.html http://www.intl.pdx.edu/EdAbroad/2006PhotoContest/Buildings%20&%20Architecture/Buildings%20&%20Arch%2 01/images/The%20Leaning%20Tower%20of%20Pisa_jpg.jpg Alternatives to Restoration
• In 1993, 600 Mg of lead weights were added to north side of Tower, attached by a removable concrete ring placed around base of Tower – Reduced leaning by nearly one minute of an arc – Reduced moment that pulled on Tower by 10% • Load was increased in 1995 to 900 Mg while engineers attempted to replace lead weights with ground anchors http://www.pubs.asce.org/ceonline/ceonline02/0302feat.html http://www.endex.com/gf/buildings/ltpisa/ltpgallery/freepix/pisaa6y.jpg?x=41&y=49 Alternatives to Restoration
• One unique idea was to drill 10,000 holes in Tower to significantly reduce its weight
• Replica was to be placed next to Tower leaning in opposite direction to hold original tower in place
http://news.bbc.co.uk/2/hi/europe/1391476.stm http://www.stilepisano.it/immagini13/ Restoration of The Tower
• A new restoration idea was presented in the 1990s – Known as soil extraction, or soil subsidence – Its goal was to excavate earth from beneath Tower’s foundation on its northern side so that Tower would tilt back toward perpendicular
• Idea was put into motion after various tests on Tower itself and on soil underneath its foundation
http://www.pubs.asce.org/ceonline/ceonline02/0302feat.html http://torre.duomo.pisa.it/towersposters/english_version/2/sezione.gif http://www.endex.com/gf/buildings/ltpisa/ltpgallery/telwpis20.gif?x=89&y=55 Restoration of The Tower
• Temporary cables attached to 3rd level of Tower – Would support Tower if anything went wrong during soil extraction
• Lead weights were attached to ends of cables to ensure that Tower would remain steady
http://www.pubs.asce.org/ceonline/ceonline02/0302feat.html http://news.bbc.co.uk/olmedia/790000/images/_793432_pisa2_300gra.gif Restoration of The Tower
• First soil extraction occurred on February 9, 1999 – Extracted by means of corkscrew drills
• At first, Tower showed no sign of rotation, but then rotated toward the North
http://www.pubs.asce.org/ceonline/ceonline02/0302feat.html http://torre.duomo.pisa.it/towersposters/english_version/10/perforazioni.gif Restoration of The Tower
• Tower had rotated seven seconds of an arc toward the North by February 23, 1999, but then it rotated back toward the South – Occurred as a result of strong, cold winds from the North – Tower soon began to rotate back toward the North after winds had diminished http://www.pubs.asce.org/ceonline/ceonline02/0302feat.html http://www.endex.com/gf/buildings/ltpisa/ltpgallery/lavori/ltpreud1498gb.jpg?x=23&y=70 Restoration of The Tower
• Soil extraction was stopped after Tower had rotated a total of eighty seconds of an arc by June 1999 • Three of the lead weights were removed in July 1999, and this resulted in a discontinuation of rotation
http://www.pubs.asce.org/ceonline/ceonline02/0302feat.html http://www.waidev2.com/php/IMAGES/HC_ThisDayInHistory/58---Image_large.jpg Restoration of The Tower
• Main soil extraction began in the year 2000, after preliminary extractions had shown vast improvement • Tower had a tendency to rotate to the East throughout the process, so soil also had to be extracted from foundation’s west side • Tower continued to move northward, and slowly the lead was removed from the structure http://www.pubs.asce.org/ceonline/ceonline02/0302feat.html http://www.endex.com/gf/buildings/ltpisa/ltpgallery/lavori/ltpreud1498gc.jpg?x=52&y=59 Restoration of The Tower
• Restoration process was finished on June 6, 2001 • Tower had returned to position it was in before 1838 • Restoration process moved Tower 1,830 seconds of an arc
http://www.pubs.asce.org/ceonline/ceonline02/0302feat.html http://www.rod.beavon.clara.net/pisa.htm Problems and Costs of Implementing • Design process cost the Italian taxpayers $25 million •Design process was complicated by decree made by Italian Government that needed to be approved regularly by Italian Parliament – Delayed restoration process – Work was halted for long periods of time
http://news.bbc.co.uk/2/hi/europe/1391476.stm http://news.bbc.co.uk/2/hi/europe/793432.stm http://www.answers.com/topic/leaning-tower-of-pisa Problems and Costs of Implementing
• Restoration process was halted when harsh winds caused Tower to rotate toward the South • Throughout restoration process, Tower had to be closed to tourists – Tourists had been able to pay a fee so they could climb Tower – Now, Pisa would lose revenue (about $2 million/yr)
http://www.endex.com/gf/buildings/ltpisa/ltpbooking.htm Problems and Costs of Implementing • Stabilization of Leaning Tower provided difficulties of its own – Tower was originally constructed on weak, compressible soil, which increased instability of Tower – Ground on south side of Tower had to be treated with delicacy because any disturbance could result in falling of Tower – Original design of Tower had to be respected throughout the process to conserve monument’s character
http://www.pubs.asce.org/ceonline/ceonline02/0302feat.html http://www.endex.com/gf/buildings/ltpisa/ltpgallery/22nov02/ltp3064rx.jpg Other Items of Interest
• There are 294 stairs to top of Tower • Leaning Tower weighs about 14,700 metric tons • About three million people visit Tower annually • There are seven bells on Tower, largest of which weighs 3.5 tons
http://www.pubs.asce.org/ceonline/ceonline02/0302feat.html http://www.endex.com/gf/buildings/ltpisa/ltpinfo.htm http://www.endex.com/gf/buildings/ltpisa/ltpgallery/22nov02/ltp3096rx.jpg Conclusion
• Restoration process was very difficult to execute – Soil on which Tower was built was very unstable – Tower’s original design had to be maintained
• Soil extraction was a successful process that saved Tower from collapse The Future of The Leaning Tower
• Speculation on whether restoration process will be beneficial in future – Professor Burland, who oversaw the restoration process, believes Tower may stay in its current condition – Professor Burland speculates that Tower may begin rotating again, and in 300 years, Tower will be where it was in 1990s • Leaning Tower was reopened to public on December 15, 2001 http://www.pubs.asce.org/ceonline/ceonline02/0302feat.html http://www.funnypictures.net.au/userimages/user1680_1165895778.JPG Works Cited
• http://www.pubs.asce.org/ceonline/ceonline02/0302feat.html • http://news.bbc.co.uk/2/hi/europe/1391476.stm • http://www.endex.com/gf/buildings/ltpisa/ltpinfo.htm • http://www.endex.com/gf/buildings/ltpisa/ltpbooking.htm • http://www.answers.com/topic/leaning-tower-of-pisa
•Images: – http://www.costruzioni.net/images/pisa.h4.jpg – http://www.electricedge.com/greymatter/archives/archive-10052003- 10112003.htm – http://www.stilepisano.it/immagini13/ – http://news.bbc.co.uk/olmedia/790000/images/_793432_pisa2_300gra.gif – http://www.endex.com/gf/buildings/ltpisa/ltpgallery/ltpgallery.htm – http://torre.duomo.pisa.it/towersposters/english_version/ – http://www.intl.pdx.edu/EdAbroad/2006PhotoContest/Buildings%20&%20Archite cture/Buildings%20&%20Arch%201/index.htm – http://www.funnypictures.net.au/userimages/user1680_1165895778.JPG